title: De novo characterization of transcriptome and gene expression dynamics in epidermis during the larval-pupal metamorphosis of common cutworm.
abstract: Larval cuticle is degraded and replaced by the pupal counterpart during larval-pupal metamorphosis in the holometabolous insects. In addition to the extrinsic transformation, the epidermis goes through significant changes at molecular levels. To elucidate the intrinsic mechanism of epidermal metamorphosis, the dynamics of chitin content in the cuticle was examined in an important agricultural lepidopteran, the common cutworm, and the transcriptome was analyzed using Illumina sequencing technology. Gene expression profiles during the metamorphosis were further studied by both the digital gene expression (DGE) system and real-time quantitative PCR. The results showed that the chitin content decreased in prepupae and then increased in pupae. A total of 58 million sequencing reads were obtained and assembled into 70,346 unigenes. Over 9000 unigenes were identified to express differentially during the transformation process. As compared with the 6th instar feeding larvae, the most significant changes took place in the proteasome and metabolic pathways in prepupae and pupae, respectively. The cytochrome P450s, VHDLs, chitinase, serine protease and genes involved in sex pheromone biosynthesis changed their mRNA levels remarkably. Three chitinolytic enzymes (chitinase, β-N-acetylglucosaminidase and chitin deacetylase) showed distinct mRNA expression patterns, the former two enzymes revealed the highest expression in prepupae, however the latter one showed its climax mRNA level in pupae. The gene expression patterns suggest that chitinase and β-N-acetylglucosaminidase may be responsible for the degradation of larval cuticles, whereas chitin deacetylase may help to degrade the pupal counterparts. Gene expression dynamics also implied that the chitin of pupal cuticle might be formed by recycling of the degraded chitin of larval cuticle rather than through de novo synthesis. The 20E-induced nuclear receptors seem to be important factors regulating chitin metabolic enzymes during the cuticle remodeling. Our data provide a comprehensive resource for exploring the molecular mechanism of epidermal metamorphosis in insects.
authors.affiliation: Guangdong Provincial Key Lab of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, 55 W. Zhongshan Ave., Guangzhou 510631, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Gu
authors.forename: Li-Xia
authors.initials: LX
authors.lastname: Huang
authors.forename: Yan-Jun
authors.initials: YJ
authors.lastname: Gong
authors.forename: Si-Chun
authors.initials: SC
authors.lastname: Zheng
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Huang
authors.forename: Qi-Li
authors.initials: QL
authors.lastname: Feng
mesh_terms: D000818:Animals; D002686:Chitin / Q000235:genetics / Q000378:metabolism; D004817:Epidermis / Q000254:growth & development / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D011679:Pupa / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018411:Spodoptera / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D059467:Transcriptome
chemical_list: D019476:Insect Proteins; D002686:Chitin
keywords: 20-hydroxyecdysone; 20E; 6L; BR-C; Broad complex; CHS; COG; CYP; Chitin; Cytochrome P450; DEG; DGE; Development; Digital gene expression; ERR; EST; EcR; EcRE; Epidermis; FDR; FTZ-F1; Fushi tarazu factor 1; GFAT; GO; GST; GlcNAc; HNF4; HR; JH; KEGG; KNI; KNRL; Knirps; Knirps-like; Kyoto encyclopedia of genes and genomes; N-acetylglucosamine; NR; Nuclear receptor; P; PP; RPKM; TLL; Transcriptome; USP; VHDL; chitin synthase; clusters of orthologous groups; differentially expressed gene; digital gene expression; ecdysone receptor; ecdysteroid response element; expression sequence tag; false discovery rate; gene ontology; glutamine-fructose-6-phosphate aminotransferase; glutathione S-transferase; hepatocyte nuclear factor 4; hormone receptor; juvenile hormone; non-redundant protein sequences; nr; nt; nuclear receptor; nucleotide; oestrogen-related receptor; prepupae; pupae; reads per kb per million reads; sixth instar larvae; tailless; ultraspiracle protein; very high density lipoprotein